Other versions exist on this site from various publications. This one is from the Radio Electronics Experimenter from 1990. The bargraph circuit uses the UAA170.
We found this circuit in the April 1988 issue of Radio Electronics magazine. The circuit can be...
Relays up to 100 mA can be driven by the 555 with the recommended circuit. The circuit is from an...
This version of the previous circuit, also from Radio Electronics magazine of July 1970, uses R4...